U.S. patent number 6,440,077 [Application Number 09/567,800] was granted by the patent office on 2002-08-27 for apparatus and method for the intravascular ultrasound-guided placement of a vena cava filter.
Invention is credited to Matthew T. Jung, Hermann W. Kaebnick, Edward V. Kinney, Richard A. Mitchell.
United States Patent |
6,440,077 |
Jung , et al. |
August 27, 2002 |
Apparatus and method for the intravascular ultrasound-guided
placement of a vena cava filter
Abstract
An apparatus and method for the intravascular placement of a
vena cava filter includes an outer sheath, an intravascular
ultrasound catheter with an ultrasonic imaging element, a guide
wire, and the vena cava filter that is to be deployed. The outer
sheath, ultrasound catheter, and guide wire share a common central
axis. The ultrasound catheter is enclosed by and is moveable
relative to the outer sheath, and the guide wire is enclosed by and
is moveable relative to the ultrasound catheter. In the stored
position, the filter is secured between the outer sheath and the
ultrasound catheter. When the apparatus is introduced into a vein,
the ultrasound catheter provides real-time imaging of the vein for
identifying the appropriate location for placement of the filter.
Once such a location has been identified, the outer sheath is drawn
back relative to the ultrasound catheter, exposing the legs of the
filter, allowing the legs of the filter to spring free and attach
themselves to the wall of the vein.
Inventors: |
Jung; Matthew T. (Louisville,
KY), Kaebnick; Hermann W. (Louisville, KY), Kinney;
Edward V. (Louisville, KY), Mitchell; Richard A.
(Louisville, KY) |
Family
ID: |
26835032 |
Appl.
No.: |
09/567,800 |
Filed: |
May 9, 2000 |
Current U.S.
Class: |
600/467 |
Current CPC
Class: |
A61F
2/0105 (20200501); A61F 2230/005 (20130101); A61B
8/12 (20130101); A61B 2090/3784 (20160201); A61F
2/011 (20200501); A61F 2002/016 (20130101); A61F
2230/0067 (20130101) |
Current International
Class: |
A61F
2/01 (20060101); A61B 8/12 (20060101); A61B
19/00 (20060101); A61B 008/14 () |
Field of
Search: |
;600/437,117,438,443,459-470 ;604/96,104,106
;606/200,194,158,198,191,199,127 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Walsh and Bettmann, Percutaneous Devices for Vena Cava Filtration,
Current Therapy in Vascular Surgery, p. 945. .
Oppat, Chiou, and Matsumura, Intravascular Ultrasound-Guided Vena
Cava Filter Placement, J Endovasc Surg 1999, pp. 285-287, vol. 6.
.
A Method for Inserting Inferior Vena Cava Filters at Bedside in
Multitrauma Patients, Vascular Surgery Outlook, 1999, pp. 17-18,
vol. 12, No. 5, Thieme Medical Publishers, Inc. .
Sing, Smith, Miles and Messick, Preliminary Results of Bedside
Inferior Vena Cava Filter Placement, Chest, Jul., 1998, pp.
315-316, vol. 114, No. 1. .
Benjamin et al, Duplex ultrasound Insertion of Inferior Vena Cava
Filters in Multitrauma Patients, The American Journal of Surgery,
Aug. 1999, pp. 92-97, vol. 178. .
Oshima, Itchhaporia and Fitzgerald, New Developments in
Intravascular Ultrasound, Vascular Medicine, 1998, pp. 281-290,
vol. 3. .
Rose, Kinney, Valji, and Winchell, Placement of Inferior Vena Caval
Filters in the Intensive Care Unit, Journal of Vascular and
Interventional Radiology, Jan.-Feb. 1997, pp. 61-64, vol. 8. .
Brigade Brachytherapy System Promotional Flier, EndoSonics
Corporation, Rancho Cordova, CA, The Netherlands and Germany. .
Simon Nitinol Filter Promotional Flier, C.R. Bard, Inc., Covington,
Georgia. .
Uren, Neal G., An Introduction to Intravascular Ultrasound, 1996,
Remedica, Hooper House, Oxford, England..
|
Primary Examiner: Lateef; Marvin M.
Assistant Examiner: Imam; Ali M.
Attorney, Agent or Firm: Stites & Harbison, PLLC Nagle,
Jr.; David W.
Parent Case Text
This application claims priority from U.S. provisional application
No. 60/137,211 filed Jun. 2, 1999.
Claims
What is claimed is:
1. An apparatus for the intravascular deployment of a filter,
comprising: a flexible outer sheath defining an outer diameter and
an inner diameter; and an intravascular ultrasound catheter
defining an outer diameter and an inner diameter, and including an
ultrasonic imaging element at a distal end thereof, said ultrasound
catheter being enclosed along a substantial portion of its length
by said flexible outer sheath, and the outer diameter of said
ultrasound catheter being less than the inner diameter of said
outer sheath, thereby allowing said ultrasound catheter to pass
through and move relative to said outer sheath; wherein, in a
stored position, said filter is secured between said outer sheath
and said ultrasound catheter near the distal end of said ultrasound
catheter; wherein, when said apparatus is percutaneously introduced
into a vein, the ultrasonic imaging element of said ultrasound
catheter generates a ultrasonic picture of the vein for identifying
an appropriate location for deployment of said filter; and wherein,
once said appropriate location is identified, said filter is
deployed through movement of said ultrasound catheter relative to
said outer sheath.
2. An apparatus for the intravascular deployment of a filter as
recited in claim 1, and further comprising a guide wire, said
ultrasound catheter defining a central channel for the passage of
said guide wire, said guide wire being first introduced
percutaneously into said vein, the outer sheath and ultrasound
catheter of said apparatus being passed over said guide wire and
into said vein for deployment of the filter.
3. An apparatus for the intravascular deployment of a filter as
recited in claim 1, wherein said filter includes a central ring
portion defining an internal diameter and a plurality of legs
secured to and extending from said ring portion; and wherein the
internal diameter of said ring portion is greater than the outer
diameter of said ultrasound catheter such that, in said stored
position, the legs of said filter are secured between said outer
sheath and said ultrasound catheter near the distal end of said
ultrasound catheter with the legs of said filter folded against and
abutting the lateral surface of said ultrasound catheter.
4. An apparatus for the intravascular deployment of a filter as
recited in claim 1, wherein said ultrasound catheter defines a
channel in a lateral surface thereof for receiving and storing said
filter, such that, in said stored position, said filter is secured
between said outer sheath and said ultrasound catheter near the
distal end of said ultrasound catheter along the lateral surface of
said ultrasound catheter.
5. An apparatus for the intravascular deployment of a filter,
comprising: a guide wire for insertion into a blood vessel; a
filter having an active state in which a plurality of filter legs
spring open and are adapted to attach to the walls of a surrounding
blood vessel; a flexible outer sheath encasing said filter in a
compressed state prior to being in an active state, said sheath
being moveable relative to said filter to permit said filter to
enter said active state; and a flexible cable moveable relative to
said sheath and having an ultrasonic imaging device near the distal
end thereof, said filter, sheath, and cable being moveable as a
unit when being inserted into said blood vessel.
6. An apparatus for the intravascular deployment of a filter as
recited in claim 5, wherein said sheath and cable have annular
cross-sections defining respective central openings, said flexible
cable positioned within the central opening defined by the annular
cross-section of said sheath.
7. An apparatus for the intravascular deployment of a filter as
recited in claim 5, wherein said flexible cable has an outer
circumferential wall with a portion thereof removed, thereby
defining a channel, said filter being positioned in said channel in
said compressed state.
8. An apparatus for the intravascular deployment of a filter as
recited in claim 6, wherein said guide wire is positioned within
the central opening defined by the annular cross-section of said
flexible cable and is moveable relative to said cable.
9. A method for the intravascular deployment of a filter using an
apparatus including a flexible outer sheath defining an outer
diameter and an inner diameter; and an intravascular ultrasound
catheter defining an outer diameter and including an ultrasonic
imaging element at a distal end thereof, said ultrasound catheter
being enclosed along a substantial portion of its length by said
flexible outer sheath, and the outer diameter of said ultrasound
catheter being less than the inner diameter of said outer sheath,
thereby allowing said ultrasound catheter to pass through and move
relative to said outer sheath; the steps of said method comprising:
introducing said outer sheath and ultrasound catheter into a vein;
positioning said outer sheath and ultrasound catheter for
deployment of said filter; moving said outer sheath relative to
said ultrasound catheter, thereby releasing said filter into said
vein; and withdrawing said outer sheath and ultrasound catheter
from said vein.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and method for the
intravascular ultrasound-guided placement of vena cava filters,
said filters often being necessary in the treatment of deep vein
thrombosis.
A deep vein thrombosis is a medical condition wherein a blood clot,
or thrombus, has formed inside a vein. Such a clot often develops
in the calves, legs, or lower abdomen, but occasionally affects
other veins in the body. This clot may partially or completely
block blood flow, and, unlike clots in superficial veins, the clot
may break off and travel through the bloodstream. Commonly, the
clot is caused by a pooling of blood in the vein, often when an
individual is bed-ridden for an abnormally long duration of time,
for example, when resting following surgery or suffering from a
debilitating illness, such as a heart attack or traumatic
injury.
Deep vein thrombosis of the lower extremities is a serious problem
because of the danger that the clot may break off and travel
through the bloodstream to the lungs, causing a pulmonary embolism.
This is essentially a blockage of the blood supply to the lungs
that causes severe hypoxia and cardiac failure. It frequently
results in death.
For many patients, anti-coagulant drug therapies may be sufficient
to dissipate the clots. For example, patients may be treated with
anticoagulants such as heparin and with thrombolytic agents such as
streptokinase. Heparin is available and marketed under such trade
names as Heparin Lock.TM., a product of Abbott Laboratories of
Abbott Park, Ill.; and Heparin Sodium.TM., a product of Pharmacia
& Upjohn of Peapack, N.J. Streptokinase is available and
marketed under such trade names as Streptase.RTM., a product of
Behringwerke Aktiengesellschaft of Frankfurt, Germany; and
Kabikinase.RTM., a product of Kabivitrum Aktiebolag of Stockholm,
Sweden.
Unfortunately, some patients may not respond to such drug therapy
or may not tolerate such therapy. For example, patients may have an
acute sensitivity to heparin or may suffer from internal bleeding
as a result of such drug therapies. Also, such drug therapies
simply may be ineffective in preventing recurrent pulmonary emboli.
In such circumstances, surgical procedures are required to prevent
pulmonary emboli. Methods for prevention of primary or recurrent
pulmonary emboli when anticoagulation therapies are ineffective are
well-defined in the prior art. The current standard of therapy for
prevention of pulmonary emboli in patients who are classified
high-risk or are unable to be anticoagulated is percutaneous
insertion and placement of an inferior vena cava filter device. A
detailed discussion of the construction and use of such filters is
contained in U.S. Pat. No. 5,893,869 issued to Barnhart, which is
incorporated herein by reference. Additional information on such
filters can also be found in an article entitled "Percutaneous
Devices for Vena Cava Filtration" by Daniel E. Walsh and Michael
Bettmann contained in Current Therapy in Vascular Surgery (3d ed.
1995) at pages 945-949; this article is also incorporated herein by
reference.
Placement of these filters is usually accomplished using either the
"femoral vein approach" or "jugular vein approach", although
alternative approaches, including "axiliary vein approaches", may
also be used. There have been a few reports of transabdominal
ultrasound being used for placement of filters, but most prior art
methods and approaches use fluoroscopy for placement of a guide
wire and catheter, as well as for placement and deployment of the
filter. Such methods for placement and deployment of a filter also
recommend the use of an intravenous dye with contrast
angiography.
The fluoroscopy unit may be employed to aid in the placement of the
filter in several different ways. For example, the patient is often
brought to a operating room or special procedures room, and a
fluoroscopy unit is used to identify bony landmarks, allowing the
physician to choose the appropriate location for the filter by
referencing the bony landmarks. When referencing bony landmarks,
placement of the filter is usually done by referencing the lumbar
third and fourth vertebrae, making an assumption that the renal
veins will be higher than this. However, this method does not
provide for an accurate definition of the vena cava size,
identification of the position of a clot or thrombus in the vena
cava, or accurate identification of the site of the renal veins. It
is important to note that, regardless of the method employed in
placing the filter, the filter must be placed below the renal
veins.
A second and much more accepted method entails the use of a fixed
C-arm or fluoroscopic C-arm guidance unit and intravenous contrast
in an inferior venacavagram to define the size of the inferior vena
cava, to identify the site of the renal veins, and to ascertain the
presence or absence of clot at the site proposed for deployment of
the filter device. Although this method is often performed in
radiology or surgical suites, rather than intensive care units, a
general discussion of this method is contained in an article
entitled "Placement of Inferior Vena Caval Filters in the Intensive
Care Unit" by Drs. Steven C. Rose, Thomas B. Kinney, Karim Valji,
and Robert J. Winchell contained in the Journal of Vascular and
Interventional Radiology, 8:61-64 (1997); this article is also
incorporated herein by reference. Deployment of the filter is then
performed per the percutaneous filter placement protocols based on
the previously performed venacavagram findings. A distinct
disadvantage of this method, however, is that the procedure must be
performed in either a special x-ray suite or a specially equipped
operating room. Thus, significant expense is involved in carrying
out this procedure, especially considering that additional staff is
often required for a special suite or an operating room. Moreover,
the necessity of this specialized location necessitates the
transport of an often critically ill or unstable patient from their
hospital room to the site of x-ray equipment.
It is therefore a paramount object of the present invention to
provide an apparatus and method for intravascular placement of a
filter that does not require the use of cumbersome and specialized
fluoroscopy equipment and/or an intravenous contrast.
It is a further object of the present invention to provide an
apparatus and method for intravascular placement of a filter that
can be performed bedside and thus does not necessitate the movement
of the patient.
It is still a further object of the present invention to provide an
apparatus and method for intravascular placement of a filter that
will substantially reduce the overall time and cost of the
placement procedure.
These and other objects and advantages of the present invention
will become apparent upon a reading of the following
description.
SUMMARY OF THE INVENTION
The apparatus of the present invention combines commercially
available surgical components into a unitary device for accurate
and effective positioning and placement of a vena cava filter. A
preferred embodiment of the apparatus of the present invention
comprises an outer sheath, an intravascular ultrasound catheter
with an ultrasonic imaging element, a guide wire, and the vena cava
filter that is to be deployed. The outer sheath, ultrasound
catheter, and guide wire share a common central axis. The
ultrasound catheter is enclosed by and is moveable relative to the
outer sheath, and the guide wire is enclosed by and is moveable
relative to the ultrasound catheter. In the stored position, the
filter is secured between the outer sheath and the ultrasound
catheter.
When the apparatus of the present invention is introduced into a
vein, the ultrasound catheter provides real-time imaging of the
vein for identifying the appropriate location for placement of the
filter. Once such a location has been identified, the outer sheath
is drawn back relative to the ultrasound catheter, exposing the
legs of the filter, allowing the legs of the filter to spring free
and attach themselves to the wall of the vein.
Such an apparatus and the use thereof obviates the need for
cumbersome and specialized fluoroscopy equipment and/or an
intravenous contrast, while also allowing filter placement to be
performed bedside, substantially reducing the overall time and cost
of the placement procedure.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a preferred apparatus made in accordance with the
present invention being positioned in a vein for deployment of a
vena cava filter;
FIG. 2 shows the proper placement of a vena cava filter directly
below the renal veins in the inferior vena cava;
FIG. 3 is a side view of a prior art filter deployment device and
associated guide wire wherein the filter is housed within a sheath
catheter;
FIG. 4 is side view of the prior art filter deployment device of
FIG. 3 wherein the filter is partially deployed;
FIG. 5 is side view of the prior art filter deployment device of
FIG. 4 wherein the filter is fully deployed;
FIG. 6 is a side view of a prior art intravascular ultrasound
catheter and associated guide wire;
FIG. 7 shows the preferred apparatus of FIG. 1 being positioned in
a vein for deployment of a vena cava filter;
FIG. 8 shows partial deployment of the vena cava filter using the
preferred apparatus of FIGS. 1 and 7;
FIG. 9 shows full deployment of the vena cava filter using the
preferred apparatus of FIGS. 1 and 7;
FIG. 10 shows the ultrasonic catheter of the preferred apparatus of
FIGS. 1 and 7 being withdrawn through the fully deployed vena cava
filter;
FIG. 11 shows the insertion and positioning of the preferred
apparatus of FIGS. 1 and 7-10 to a proper position below the renal
veins in the inferior vena cava;
FIG. 12 shows the proper placement of a vena cava filter using the
preferred apparatus of FIGS. 1 and 7-10 directly below the renal
veins in the inferior vena cava;
FIG. 13 is a side view of the preferred apparatus of FIGS. 1 and
7-10 with the outer sheath cut away to show the position of the
filter within the sheath;
FIG. 13A is a top sectional view of the filter depicted in FIG. 13
taken along lines 13A--13A of FIG. 13;
FIG. 14 is a top sectional view of the preferred apparatus of FIGS.
1 and 7-10 taken along lines 14--14 of FIG. 8;
FIG. 15 is a side view of a second preferred apparatus made in
accordance with the present invention; and
FIG. 15A is a top sectional view of the filter depicted in FIG. 15
taken along lines 15A--15A of FIG. 15.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention relates to an apparatus and method for the
intravascular ultrasound-guided placement of vena cava filters.
Referring first to FIG. 2, this Figure depicts the appropriate
placement of a vena cava filter 10 directly below the renal veins
64, 66 in the inferior vena cava 60. Great care must be taken to
define the anatomy of this area prior to deployment to avoid
encroachment on the renal veins 64, 66 and to ascertain the absence
or presence of clots in the vena cava 60. Also, the attending
physician must ensure that the vena cava 60 has the appropriate
inner diameter for receiving the filter, typically between 10 to 20
mm, and no greater than 28 mm.
FIGS. 3-5 show a typical prior art filter 10 and the deployment
device 12 for placement of the filter 12. Generally, the deployment
device 12 includes a sheath catheter 14 over a guide wire 16. The
filter 10 to be deployed is loaded into the distal end of the
sheath catheter 14. The catheter 14 is inserted into a vein, and
then appropriately positioned using a fluoroscopy unit or other
method, as described above. Once so positioned, the outer sheath of
the catheter 14 is retracted, allowing the filter 10 to spring open
and attach to the walls of the vein. The catheter 14 and guide wire
16 are then withdrawn and removed. Placement of these filters is
usually accomplished using fluoroscopy and a contrast angiography.
As described above, one common method entails the use of a fixed
C-arm or fluoroscopic C-arm guidance unit and intravenous contrast
in an inferior venacavagram to define the size of the inferior vena
cava, to identify the site of the renal veins, and to ascertain the
presence or absence of clot at the site proposed for deployment of
the filter 10. Deployment is then performed per the percutaneous
filter placement protocols based on the previously performed
venacavagram findings.
FIG. 6 of the present application depicts a common prior art
intravascular ultrasound catheter (IVUC) 20. Such a catheter is
commonly an extruded plastic sheath having a circumferential wall
enclosing and protecting the internal wiring and circuitry of the
IVUC 20. This particular IVUC includes a solid state imaging
element 22. Such IVUCs 20 can provide high quality, real-time
imaging of the internal walls of a blood vessel and thus are
commonly used in the diagnosis and treatment of fully or partially
blocked arteries of the heart, often through the use of an IVUC 20
in conjunction with a percutaneous transluminal coronary
angioplasty (commonly referred to as "balloon angioplasty"). For a
general discussion of intravascular ultrasound catheters and their
use in angioplasty, see U.S. Pat. No. 5,749,848 issued to Jang, et
al. and assigned to Cardiovascular Imaging Systems, Inc. of
Sunnyvale, Calif. This patent is incorporated herein by
reference.
Referring again to FIG. 6, the ultrasonic imaging element 22 that
generates the cross-sectional imaging of a blood vessel is housed
in the tip of the catheter 20. Signals from the ultrasonic imaging
element 22, indicative of reflected ultrasonic waves, are
transmitted through internal wires within the catheter 20 to a
signal processor.
The design and construction of intravascular ultrasound catheters
is well-known in the art. For example, one such IVUC is described
in U.S. Pat. No. 4,917,097, issued to Proudian, et al. and assigned
to the Endosonics Corporation of Cordova, Calif. This patent is
incorporated herein by reference. The present invention does not
seek to redesign or improve upon the construction of such
catheters, whether they be solid state or mechanical in nature, but
rather seeks to employ a intravascular ultrasound catheter in a new
and unique apparatus and method for using said apparatus. Indeed,
it is contemplated that the apparatus and method of the present
invention be carried out by using a commercially available IVUC,
such as the EndoSonics.RTM. phased array solid state catheter with
central wire or the ClearView Ultra.TM. Intravascular Ultrasound
System manufactured and distributed Boston Scientific Corporation
of Natick, Mass.
FIGS. 13, 13A and 14 depict a first preferred embodiment of the
apparatus of the present invention. This apparatus 40 combines
commercially available surgical components into a unitary device
for accurate positioning and placement of a vena cava filter 50. As
shown in FIGS. 13 and 14, this preferred apparatus 40 is comprised
of an outer sheath 42, an IVUC 44 with an ultrasonic imaging
element 46, a guide wire 48, and the vena cava filter 50 that is to
be deployed.
The outer sheath 42 is preferably an 8.0 Fr flexible sheath. The
sheath 42 depicted in FIGS. 13 and 14 is part of the Super
Arrow-Flex.RTM. Percutaneous Introducer Set, Product No. CL-07865,
manufactured and distributed by the Arrow International Investment
Group of Wilmington, Del. This product is licensed under U.S. Pat.
No. 5,180,376 issued to Fischell, which is incorporated herein by
reference. As shown, this particular sheath 42 has a wall 41
comprised of a flexible, helical metal coil. The wall 41 is then
covered in a thin layer of plastic material 43. Furthermore, the
particular sheath 42 has an associated, tapered dilator (not shown)
at its distal end for percutaneous insertion of the sheath 42 into
the vein. However, the present invention does not require such a
dilator as the tapered distal end of the IVUC 44 could serve as an
appropriate dilator for percutaneous insertion of the sheath 42 and
IVUC 44.
The IVUC 44 preferably has a diameter of approximately 6.0 Fr,
allowing it to be easily manipulated and passed through the outer
sheath 42. As shown, the IVUC 44 has a solid state imaging element
46, although a mechanical or rotating mirror imaging element could
be used without departing from the spirit and scope of the present
invention. Again, the present invention does not seek to redesign
or improve upon the construction of ultrasonic catheters, whether
they be solid state or mechanical in nature, but rather seeks to
employ a intravascular ultrasound catheter in a new and unique
apparatus and method for using said apparatus.
Finally, the guide wire 48 is preferably a J-tipped or curved wire
with a Teflon.RTM. coating or similar lubrication. Such coating
facilitates smooth movement of the guide wire 48 within a blood
vessel, thereby minimizing the hazards of blood clot generation and
trauma to internal tissues. In this preferred embodiment, the
approximate diameter of this guide wire 48 is 0.035 inches,
allowing it to be easily manipulated and passed through the IVUC
44.
The filter 50 itself could be a modified version of a number of
commercially available vena cava filters, the only requirement
being that the filter 50 have a ring portion 52 at its apex so that
it the IVUC 44 may pass through the filter 50. Such a construction
of the filter 50 is depicted in FIGS. 13, 13A and 14.
As clearly shown in FIGS. 13 and 14, the outer sheath 42, IVUC 44,
and guide wire 48 share a common central axis. Thus, the IVUC 44 is
enclosed by and is moveable relative to the outer sheath 42, and
the guide wire 48 is enclosed by and is moveable relative to the
IVUC 44. In other words, the outer sheath 42 has an annular
cross-section and defines an inner diameter. This inner diameter is
slightly greater than the outer diameter of the IVUC 44. Similarly,
the IVUC 44 has an annular cross-section and defines an inner
diameter. This inner diameter is slightly greater than the outer
diameter of the guide wire 48. In this regard, as noted above, it
is preferred that the distal end of the IVUC 42 be tapered to serve
as an appropriate dilator.
The filter 50 slides over the IVUC 44 with the ring portion 52 of
the filter 50 resting just below the ultrasonic imaging element 46
of the IVUC 44. In the stored position, the legs 51 of the filter
50 are folded down against the IVUC 44 and are secured between the
outer sheath 42 and the IVUC 44. In this regard, although not
shown, the IVUC 44 may be provided with a circumferential lip or
similar protrusion upon which the filter 50 may rest.
A better understanding of the construction of the apparatus 40 of
the present invention can be achieved through a review of the
function and operation of the apparatus 40. Referring first to FIG.
1, a thrombus 61 is present in the right femoral vein 62. As
indicated by the arrows, blood flows from the femoral veins 62
through the vena cava 60 toward the heart and lungs, and thus
placement of a vena cava filter 50 (not shown) is necessary to
prevent the thrombus 61 from traveling to the heart and lungs
should it break free.
To deploy the vena cava filter 50 using the preferred apparatus 40,
the guide wire 48 is inserted into the vena cava 60, preferably
using the Seldinger technique from the femoral position. Over the
guide wire 48, the outer sheath 42 and IVUC 44 are passed
percutaneously through the femoral vein 62 and into the vena cava
60. In this regard, there is preferably a coupling, as indicated by
reference numeral 39 in FIG. 1, that is secured to a distal end of
the outer sheath 42. This coupling has an internal seal (not shown)
that maintains the positions of the outer sheath 42 and the IVUC 44
relative to one another, thus allowing the outer sheath 42 and the
IVUC 44 to be moved together as a unit. When it is necessary to
move the IVUC 44 relative to the outer sheath 42, the attending
physician must physically maintain the position of the coupling 39
while manually advancing the IVUC 44 through the coupling 39; or,
the attending physician may physically maintain the position of the
IVUC 44 while drawing back the outer sheath 42 and coupling 39
relative to the IVUC 44.
As best shown in FIG. 11, as it travels through the femoral vein 62
and into the vena cava 60, the ultrasonic imaging element 46 of the
IVUC 44 provides a real-time ultrasonic picture of its passage,
thereby assuring proper placement of the filter 50. In this regard,
the ultrasonic signals received by the ultrasonic imaging element
46 are transmitted through internal wiring 45 of the IVUC 44 to an
external signal processor (as indicated in phantom and by reference
numeral 47 in FIG. 1). This real-time imaging of the veins also
allows for measurement of the inner diameter of the vena cava 60
and provides a visual confirmation that there is no thrombus in the
area selected for deployment of the filter 50. Finally, the
ultrasonic imaging allows for extremely accurate identification of
the position of the renal veins 64, 66 to further ensure
appropriate placement of the filter 50. In this regard, it is
preferred that the outer sheath 42 and IVUC 44 are moved through
the vena cava 60 past the renal veins 64, 66 (as indicated in
phantom in FIG. 11) so that the attending physician can view the
portions of the vena cava 60 adjacent the renal veins 64, 66. The
outer sheath 42 and IVUC 44 are then drawn back to an appropriate
position below the renal veins 62, 64 for deployment of the filter
50. After deployment of the filter 50, the preferred apparatus 40,
sans the filter 50, is withdrawn from the vena cava 60, as shown in
FIG. 12.
FIGS. 7-10 demonstrate, in greater detail, the deployment of the
filter 50 using the preferred apparatus 40 described above. As
shown in FIG. 7, in its stored position, only the ring portion 52
of the filter 50 extends beyond the distal end of the outer sheath
42. The ultrasonic imaging element 46 of the IVUC 44 extends just
beyond the ring portion 52 of the filter 50, or in front of the
filter 50. The positioning of the ultrasonic imaging element 46 of
the IVUC 44 in front of the filter 50 provides for a clear,
unobstructed ultrasonic picture of the femoral vein 62 (as shown in
FIG. 11) and vena cava 60 as the preferred apparatus 40 is moved
through the veins and into position for deployment of the filter
50. Again, this real-time ultrasonic imaging of the veins also
allows for measurement of the inner diameter of the vena cava 60
for appropriate placement of the filter 50, and provides a visual
confirmation that there is no thrombus in the area selected for
deployment of the filter 50.
Referring now to FIG. 8, once the appropriate location for
deployment of the filter 50 has been identified, the outer sheath
42 is drawn back relative to the IVUC 44. In other words, the outer
sheath 42 is retracted while the position of the IVUC 44 is
maintained. This exposes the legs 51 of the filter 50. Once the
outer sheath 42 has been sufficiently retracted, the legs 51 of the
filter 50 spring free and attach themselves to the wall of the vena
cava 60, as shown in FIG. 9.
With the filter 50 in place in the vena cava 60, the IVUC 44 can be
withdrawn through the filter 50, as shown in FIG. 10. As the IVUC
44 is withdrawn, the real-time ultrasonic imaging is used to
evaluate the filter 50 to ensure that the struts and hooks of the
filter 50 have properly attached to the walls of the vena cava
60.
FIGS. 15 and 15A depict a second preferred embodiment of the
present invention, an embodiment which is considered the best mode
for carrying out the invention. This preferred apparatus 40A is
similarly comprised of an outer sheath 42A, an IVUC 44A with an
ultrasonic imaging element 46A, a guide wire 48A, and the vena cava
filter 50A that is to be deployed.
Again, the outer sheath 42A is preferably an 8.0 Fr flexible sheath
which has a wall 41A comprised of a flexible, helical metal coil
encased in a thin layer of plastic material 43A. The IVUC 44A
preferably has a diameter of approximately 6.0 Fr, allowing it to
be easily manipulated and passed through the outer sheath 42A.
Finally, he guide wire 48A is preferably a J-tipped or curved wire
with a Teflon.RTM. coating or similar lubrication, and having a
diameter of approximately 0.035 inches, allowing it to be easily
manipulated and passed through the IVUC 44A.
In this preferred embodiment, rather fitting over and around the
IVUC 44A, a portion of the side wall of IVUC 44A is removed to
provide a channel 55A for accommodating the filter 50 alongside the
IVUC 44A. The filter 50A is loaded into this channel 55A and stored
in this channel 55A between the outer sheath 42A and the IVUC 44A
for deployment. The primary advantage to such a construction is
that no modification of existing filter designs in necessary.
Virtually any existing filter can be incorporated into this
preferred embodiment. For example, a Simon Nitinol Filter.RTM.,
which is a popular filter available through C.R. Bard, Inc. of
Covington, Ga., could be easily incorporated into the apparatus of
the present invention. Moreover, existing intravascular ultrasound
catheters can be incorporated into this preferred embodiment with
only minimal modification of the shaft of the catheter, as
described above, and with no change or modification of the
functioning components of the IVUC, particularly the ultrasonic
imaging element 46A.
Again, deployment of the filter 50A is achieved through proper
positioning of the apparatus 40A based on the ultrasonic picture of
the vena cava generated by the ultrasonic imaging element 46A of
the IVUC 44A, followed by retraction of the outer sheath 42A
relative to the IVUC 44A. Such retraction of the outer sheath 42A
exposes the legs 51A of the filter 50A, thereby allowing the legs
51A of the filter 50A to spring free and attach themselves to the
wall of the vena cava 60. As the filter 50A springs open, it is
possible that the IVUC 44 itself may interfere with deployment of
the filter 50A. For example, one of the legs 51A of the filter 50A
could be caught up in the channel 55A. However, forward and
rearward movement of the IVUC 44 relative to the vena cava 60
should free the filter 51A for full deployment. As with the first
preferred embodiment described above, with the filter 50A in place
in the vena cava, the IVUC 44A can be withdrawn through the filter
50A. And, as the IVUC 44A is withdrawn, the real-time ultrasonic
imaging is used to evaluate the filter 50A to ensure that the
struts and hooks of the filter 50A have properly attached to the
walls of the vena cava.
Each of the above described apparatus could be developed and
manufactured using a combination of currently available,
FDA-approved intravascular ultrasound catheters, guide wire
catheters, introducers and sheaths, and filters. However, it is
contemplated that other devices could be developed and used in
practicing the present invention without departing from the spirit
and scope of the present invention.
As the foregoing description makes clear, there are numerous
advantages to the apparatus and methods described above. A primary
advantage would be the decreased cost involved in placing filters
using ultrasonic imaging rather than fluoroscopy. As mentioned
above, fluoroscopy procedures are extremely expensive, often
requiring operating room time and specialized staffing. Also, the
number of wires and catheters needed for ultrasonic placement as
described herein is significantly less than prior art
procedures.
Another important advantage is that the apparatus and methods
described herein are inherently safer for both patients and staff.
Since x-ray equipment is not needed, the patient and staff are not
exposed to the dangers of x-ray radiation. Also, an intravenous
contrast is not necessary; thus, the patient is not exposed to the
risk of anaphylactic shock and death from contrast reaction.
Finally, since the procedures described herein can be performed at
bedside, critically ill or unstable patients need not be
transported. While being transported through poorly or
lesser-equipped areas of a hospital, such as an elevator or the
radiology suite, emergency situations, such as oxygen desaturations
or arrhythmia, are more difficult to deal with because of the lack
of experienced personnel and the lack of accessibility to
appropriate medications and therapies.
It will be obvious to those skilled in the art that modifications
may be made to the preferred embodiments described herein without
departing from the spirit and scope of the present invention.
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